1. Field of the Invention
The present invention relates to plastic caps for closing container neck openings, and has particularly advantageous use with widemouthed plastic containers of the type commonly used to dispense small quantities of such viscous substances as ointments and the like.
2. Prior Art
Widemouthed plastic containers are used extensively to dispense small quantities of viscous substances such as petroleum jelly, cosmetics, creams, ointments and the like. The containers are usually substantially rectangular, when viewed in horizontal cross-section, and provide an elongated neck opening bounded by two relatively long side walls and two relatively short side walls. The long side walls are frequently slightly curved to increase the central width of the neck opening. One or both pairs of side walls are commonly provided with laterally extending protrusions on their outer surface to assist in retaining a cap on the container neck.
Proposals to provide containers of this type with inexpensive snap-on, snap-off caps have presented a number of drawbacks. A problem common to all known prior proposals is the tendency of their caps to dislodge relatively easily, whereby the contents of the container are exposed if the container is jossled about or dropped. This problem is particularly annoying when container caps dislodge while the containers are being transported in one's luggage.
An approach common to most previous proposals is the use of a stamped metal cap having skirt-wall projections which extend toward and are intended to cooperate with neck-carried protrusions to hold the cap in place on a container neck. While the resulting cap structure is quite rigid and tends to tightly clamp portions of the container neck, the problem remains that the neck portions are relatively flexible and tend to deflect inwardly when the container is jossled about or dropped, thereby releasing the clamping action of the container cap and permitting it to dislodge.
A problem with the use of stamped metal caps is that they are relatively expensive to fabricate. As a safety precaution, the bottom rim of their skirt walls is usually rolled over to shield sharp edge surfaces, and this rolling step adds to the cost of the cap. The skirt-carried cap-retaining projections are usually formed by stamping depressions into opposite side walls of the skirt, and this operation also adds to the cost of the cap.
Still another drawback of stamped metal caps for widemouthed containers is that the depressions formed in opposite side walls detract from the appearance of the cap. These required depressions taken together with the need for a rolled rim at the base of the cap foreclose the possibility of providing a cap which has smooth outer walls and a clean, crisp appearance. Difficulties encountered in getting skirt-carried depressions and projections to function properly in retaining stamped metal caps on widemouthed containers has, in fact, lead to the use of very wide, long depressions and projections, which detract very noticeably from the appearance of the caps.
A further problem with previously proposed cap retaining systems for use with widemouthed containers is that their mechanisms tend to lessen in effectiveness with repeated use. This tendency toward diminished effectiveness is frequently coupled with a further diminution in cap-retaining capability caused by the lubricating action of the contents of the container forming a film coating the cap retaining projections and protrusions. As a result, it is not at all unusual to find the snap-cap containers of experienced travelers thoroughly taped to prevent their caps from dislodging during transit.
Still another problem encountered with previously proposed cap constructions for widemouthed containers is that they do little if anything to facilitate the nested stacking of a plurality of containers on drug store shelves and the like. To the extent that proposed cap constructions do attempt to facilitate stacking of containers, they do little if anything to maintain an aligned arrangement of the fronts of the containers so that container labels remain aligned to form an attractive display. If a druggist makes a stacked display of the containers, as he must to conserve valuable shelf space, he finds that proposed containers slide easily atop each other and assume unaligned positions which not only detract from the appearance of the display but also frequently contribute to displayed containers being upset or dropped by customers. This not only results in container damage, but also frequently causes the container caps to dislodge, thereby exposing container contents.